Poly(ethylene terephthalate), herein abbreviated PET, is widely used in many materials and products, such as fibers, fabrics, molding resins, and soda bottles. Most of these uses require a polymer of relatively high molecular weight. Such polymers have been commercially made by raising, either in melt or solid-state polymerization, the molecular weight of a prepolymer or oligomer.
Melt polymerizations require higher temperatures, which is more likely to cause polymer decomposition, and expensive equipment. Solid-state polymerizations, in contrast, are usually run at somewhat lower temperatures. Solid-state polymerizations also have the advantage, compared to melt polymerizations, that very high molecular weights, where melt viscosities would otherwise be extremely high, can be more readily obtained. In commercial use, however, solid-state polymerizations may be relatively slow. Furthermore, solid-state polymerizations usually require that the lower molecular weight PET, in the form of particles or pellets, undergo a relatively lengthy crystallization process prior to being polymerized in the solid-state. Therefore, better polymerization methods for PET are desired.
N. S. Murthy, et al., Polymer, vol. 31, p. 996-1002; C. M. Roland, Polym. Eng. Sci., vol. 31, p. 849-854; and A. Siegman, et al., J. Polym. Sci., Polym. Phys. Ed., vol. 18, p. 2181-2196 (1980) all report on the properties, particularly the crystalline properties, of various PET polymers. None of these polymers disclose or teach the novel form of PET, and their associated properties, claimed herein.
U.S. Pat. Nos. 3,405,098, 3,544,525, 4,064,112, 4,165,420, 4,254,253, and 4,271,287, and F. Pilati in G. Allen, et al., Ed., Comprehensive Polymer Science, Vol. 5, p. 201-216 (Pergamon Press, Oxford 1989) describe various aspects of solid-state polymerization and/or the preparation of PET for use in solid-state polymerization. None of these patents or references discloses the novel processes or compositions of the present invention.